The present invention relates to a device for adjusting a throttle valve (1) which is mounted in the intake connection (2) or manifold of an internal combustion engine, the device comprising
a cable pulley (8) which can be displaced, against the force of a first return spring (3), between an idle operation stop (4) and a full-load stop (5) by means of a gas pedal (6) and a rod or cable (7) and can be coupled to the shaft of the throttle valve (1a), PA1 an electromotive actuating drive (9) with gearing and clutch (10), PA1 an electronic control device (11), PA1 a throttle valve (1) which can turn against the force of a second return spring (12) and has a first lever (13) connected, fixed for rotation, to the throttle-valve shaft (1a) for coupling to the pulley (8), and a second lever (14) connected, fixed for rotation, to the throttle-valve shaft (1a) for coupling to an actuating drive, as well as PA1 a coupling member (15) between pulley (8) and the first lever (13). PA1 a) the return spring (3) acts directly on the pulley (8); PA1 b) the coupling member (15) is urged by a coupling spring (16) against the first lever (13) of the throttle-valve shaft (1a); and PA1 c) a third return spring (19) acts on the driven shaft (18) of the actuating drive (9).
A device of this type is known from VDI Report No. 819 (1990), pages 741-763. In that case, the coupling member between pulley and the first lever, which is rigidly attached to the throttle-valve shaft, is urged by means of a spring (F.sub.R1A and F.sub.R1B) in the idling direction of the throttle valve towards the pulley. Furthermore, two stops are provided on the coupling member in order to define the idle control range (LLR range). The first lever, which is rigidly attached to the throttle-valve shaft, is movable back and forth between these stops by the cooperation of the electromotive actuating device with the return spring (F.sub.R3) without the coupling member changing its position. In other words, when the gas pedal is completely released and the coupling member lies against the idle stop, regulation of the throttle valve position between the smallest possible and largest possible idle positions (LL.sub.min, LL.sub.max) can be effected via the electromotive actuating drive as determined by the electronic control device. However, if it is desired to use the known device also for the electromotive control of the position of the throttle valve between idle and full load, i.e. for the automatic actuating of a predetermined speed (without use of the gas pedal), then the actuating drive must be sufficiently strong also to tension the return spring on the coupling member, two of which springs are provided for the sake of redundancy (F.sub.R1A, F.sub.R1B). The drive in the known device had to be designed for a torque about 50 to 60% greater than in the case of a pure idle control. In other words, it was necessary to provide a correspondingly larger drive motor, a larger gearing, and a stronger coupling, which necessarily results in a larger overall volume and a greater weight.
Furthermore, a larger electromotive actuating drive also affects the design of the return springs, as a result of which further enlargement of the electromotive actuating drive may be necessary.